Steam system

ABSTRACT

A winterized steam propulsion system which utilizes water as the working fluid and which comprises a boiler, an expander, a feed pump, and a condenser has water storage means which provides, substantially immediately on demand, at ambient temperatures below the freezing point of water, a supply of non-frozen water at least sufficient to charge the boiler, and means for utilizing the steam produced from the non-frozen water supply to place the system in full operation.

United States Patent 1 Gerstmann et al.

[451 July 24, 1973 STEAM SYSTEM Inventors: Joseph Gerstmann, Sudbury;

Richard S. Morse, Wellesley; Lawrence C. Hoagland, Concord, all of Mass.

Steam Engine Systems, Inc., Newton, Mass.

Filed: Jan. 29, 1971 Appl. No.: 110,857

Assignee:

US. Cl 60/1, 60/107, 137/341 Int. Cl. F0lk 15/02, F0lk '27/00 Field of Search .L 123/41.14; 165/105;

References Cited UNITED STATES PATENTS Barlow 123/41.14

1,632,596 6/1927 Grantier 123/41.14 3,468,300 9/1969 Geyer et a1. 165/105 X 3,563,035 2/1971 Raymond 60/107 X Primary Examiner-Martin P. Schwadron Assistant Examiner-Allen M. Ostrager Attorney-Edgar H. Kent [57] ABSTRACT A winterized steam propulsion system which utilizes water as the working fluid and which. comprises a boiler, an expander, a feed pump, and a condenser has water storage means which provides, substantially immediately on demand, at ambient temperatures below the freezing point of water, a supply of non-frozen water at least sufficient to charge the boiler, and means for utilizing the steam produced from the non-frozen water supply to place the system in full operation.

24 Claims, 14 Drawing Figures PATENIED M24375 sum 10F 4 FIG. 2

PATENIED SHEEYJOFd FIG l2 PAIENIELJmwm 3.747. 333

saw Mr 4 FIG. 9

STEAM SYSTEM This invention relates to steam propulsion systems and, particularly, to vehicular steam engines.

Recent interest in steam, particularly for the propulsion of passenger vehicles, trucks and busses, has been stimulated by the relatively low emissions, i.e., hydrocarbons, carbon monoxide, and oxides of nitrogen, which are generated by an external combustion boiler of the type normally associated with steam generators of advanced design. Although organic liquids have been suggested as in Rankine cycle piston type turbine engines, the thermodynamic properties of water render it the preferred fluid for a positive displacement type Rankine engine system. Moreover, whereas the typical decomposition of organic liquids at elevated temperatures makes it unlikely that any organic material could be utilized in such a Rankine system at temperatures above 550F, water is extremely stable, steam being currently used in large steam turbines at temperatures in excess of I200F. Such superherheated water vapor results in improved engine efficiency. Finally, water is non-toxic, non-flammable, substantially non-corrosive at high purity levels, readily available and inexpensive.

The primary disadvantage of water in a Rankine cycle engine is its high freezing temperature relative to the expected low ambient temperatures (as low as 40F) at which the equipment may be expected to up erate. To cycle an antifreeze along with the water, however, would introduce great complications into the system since not only would the corrosiveness and toxicity of the component have to be accounted for, but also the tendency of organic antifreezes to decompose could be compensated safely only by running the system at very inefficient low temperatures.

. The object of this invention is to provide a winterized steam propulsion system,'using essentially pure water as a working fluid,which is capable of both easy startup and continuous operation at temperatures substantially 'below the freezing point of the water used in the system. i

v, Another object is to providea low noise, low pollution Rankine cycle steam propulsion system useful for operating trucks, busses, boats, off-road vehicles, and similar systems over a wide range of ambient temperatures. i I I In accordance with the invention, a steam propulsion system comprising a'boiler, an expander and a condenser, and utilizing water as a working fluid, is winterized by providing in said system: first water storage means having the capacity to contain water frozen therein without damage; second water storage means provided'with means to provide substantially immediately on demand at ambient temperatures below the freezing point of water a supply of non-frozen water at least sufficient to charge the system boiler; means operative on shutdownof said system to store substantially all the water needed for continued operation of said system in said second storage means and to store substantially all the remainder of such water in said first storage means; means operative on startup after shutdown at ambient temperatures below the freezing point of water to fire system boiler and to pass thereto the supply of non-frozen water from the second storage means; and, means for utilizing the heat of steam produced from the non-frozenwater supply by the boiler to thaw frozen water in the first storage means and to place the system in full operation. If all of the water in the second storage means is maintained non-frozen, then water from this storage means is immediately fed to the boiler, and the entire system is started up as soon as the required steam pressures are reached. If some of the water in the second storage means is allowed to freeze during shutdown, the heat produced by the steam formed in the boiler from the non-frozen water supply is used to thaw more water until an adequate system liquid water supply is achieved for starting the entire system. If all of the water in the second storage means ia allowed to freeze, then means are provided for selectively thawing only a supply of water sufficient to charge the boiler, and the remaining water is then thawed by the steam from this initial charge. The steam first produced by the boiler may also be used to thaw or warm-up various system components by providing warm-up conduits in those components.

If the second storage means is provided at the low point of the system, water may be gravity drained from the system into the storage means. It is also preferred to provide valve means for isolating the second storage means from the remainder of the system during shutdown, so as to prevent water migration by evaporation or sublimation out of the second storage means to colder regions of the system after shutdown.

In one embodiment, a heater is provided, which may be thermostatically controlled in response to a water temperature sensor during shutdown, to heat (preferably intermittently) some or all of the water in the second storage means during shutdown so as to maintain water non-frozen. This heater may be itself electrical,

or may be fuel-burning but electrically ignited-in either event, the required power can be supplied simply from a conventional vehicle electric storage battery. In one heater arrangement, a hermetically sealed tubular member containing a vaporizable liquid such as water is disposed with its upper end in the second storage means, and its lower end outside of the second storage means and arranged to be heated. The heat boils the liquid in the lower end of the pipe, forming vapor which heats the upper pipe walls (which in turn heat the sump water), condenses, and runs back down the walls to be boiled again. The tubular member is constructed with a liquid flow path between the ends ensuring drainage of condensed water back to the lower end of the member. The water storage means associated with such a heater preferably contains a barrier of thermal insulating material (e.g., a 1 to 2 inch thickness of polyurethane foam) substantially enclosing the water therein, with the tubular heating element protruding through this barrier and so arranged that, when not' being heated, the vaporizable liquid in said element will be in a region of the element which is outside of the water storage means.

In another embodiment, an antifreeze additive is ad containing only water. During shutdown, at least a boiler charge of separable water is contained in the first compartment. The water in the second compartment may be allowed to freeze therein, or may be passed (e.g., by gravity) by a thermostatically controlled valve to the first compartment when it reaches a dangerously low temperature to avoid freezing. In startup, pure water separated from the first compartment (as by distillation) is passed through the boiler, then condensed in the condenser, and fed to the second compartment until sufficient pure water is contained in the second compartment to startup and operate the entire system. Then the first compartment is replaced in the boilercondenser cycle by the second compartment for the remainder of operation.

In a further embodiment, the second storage means in constructed to have first and second storage compartments, of which the first is constructed to contain frozen water without damage and has a water capacity at least sufficient to charge the boiler, and thawing means are provided in the system for thawing water frozen in this compartment on demand. For example, this first storage compartment can have the form of a resiliently compressibe electroconductive tube sized to contain a supply of water for charging the boiler, which is filled on shutdown with water which isallowed to freeze. On demand, current is passed through the tube to thaw the water substantially immediately to provide the non-frozen water supply for the boiler. The steam so produced is used to thaw the remaining water in the second storage compartment. In one embodiment, the tube is contained in an airtight container which is pressurized to collapse the tube and thereby force the thawed water therein to the boiler.

In another aspect, the invention features a winterized steam propulsion system which is at least partially drainablee.g., having at least a boiler and feed pump which are drainable, and which comprises water storage'means arranged at the lowpoint of the system and sized to contain the drainable water of the system, and drain means, including conduit means arranged to connect the water storage means with the drainable system components, and valve means adapted, upon actuation, to isolate the water storage means from the drainable components; this drain means is automatically operably during shutdown of the system to drain the-drainable components through the conduit means into the water storage means, and thereafter to actuate the valve means to isolate the water storage means; and, the water storage means includes also means to provide substantially on demand, at ambient temperatures below the freezing point of water, the supply of nonfrozen water to charge said boiler as previously described.

Other objects, features and advantages will be apparcut to one skilled in the art from the following description of preferred embodiments of the invention taken together with the attached drawings thereof, in which:

FIG. 1 is a diagrammatic, flow-sheet type illustration of a steam propulsion system embodying the present invention;

FIG. 2 is an enlarged sectional, diagrammatic view, partially broken away, of the sump and sump heater assembly of FIG. 1, along the line 2--2 of FIG. 3;

FIG. 3 is another sectional, diagrammatic view of the sump and sump heater assembly of FIG. 1, along the line 33 of FIG. 2;

FIG. 4 is a sectional, diagrammatic view of a water line useful in the steam propulsion systems of this invention;

FIGS. 5a and 5b are perspective views of water container structure useful in the steam propulsion systems of this invention, the container containing liquid water in FIG. 5a and ice in FIG. 5b;

FIGS. 6a and 6b are sectional, diagrammatic views of another water line useful in the steam propulsion sys' tems of this invention, the line of FIG. 6a containing liquid water and the line of FIG. 6b containing ice;

FIG. 7 is a perspective view of another water container structure useful in the steam propulsion systems of this invention;

FIG. 8 is a diagrammatic flow sheet-type illustration of another steam propulsion system embodying the present invention;

FIG. 9 is a diagrammatic flow sheet-type illustration of still another steam propulsion system embodying the present invention;

FIG. 10 is a bottom diagrammatic view of the water container of another sump embodying the present invention;

FIG. 11 is a sectional view of the container of FIG. 9 along the line l0l0 of FIG. 9; and,

FIG. 12 is a diagrammatic flow sheet-type illustration of another steamgenerating system embodying this invention.

FIGS. 1, 2 and 3 show diagrammatically a Rankine cycle steam propulsion system 10 in which water fed by a drainable feed pump 12 (e.g., a piston pump) is vaporized in boiler 14 (which includes the usual blower, air and fuel pumps, only the fuel atomizing air pump being shown at 15), fired by burner 16, fed as steam through throttle valve 18 to adiabatic expander 20, and returned through condenser 22 for recycling. A fuel supply 24 includes a fuel container for supplying a suitable fuel (kerosene, No. 1 fuel oil, etc.) to burner 16 through valve 25, as well as a conventional fuel pump. The expander is linked in the usual manner to drive a vehicle or other apparatus. Feed pump 12 may be run by the expander or associated engine linkages. The system also includes a storage battery (e.g. a conventional 12 volt, amp-hour lead acid storage battery) in the usual manner.

To provide for system. shutdown at sub-freezing temperatures, there is provided a sump container 32 with sloping side walls 33 constructed to allow for upward expansion of water should freezing occur, and surrounded by a barrier layer 34 of thermal insulation (e.g., a 1 to 2 inch thickness of a synthetic foam such as polyurethane foam). Sump container 32 also has an expandable inner wall or bladder 35, which is sealed around its edges, and the outer side of which is in communication with an air inlet port 36, to which air from pump 15 may be admitted through air line 37 and valve 38. Sump container 32 is in communication through feed line 39, feed valve 40, and water pump 41 .with water tank 42 which is also constructed with sloping side walls so as to tolerate freezing of the enclosed water without rupture, and which may have a layer 42a of thermal insulation of the type provided for sump container 32. Although the water capacity of sump container 32 is sufficient for operation of the system, even for substantial periods of time, eventual leakage from the system (e.g., through the conventional condenser bleed valves) will require makeup water, such as is conveniently contained in the water tank 42. Conduit 43 provides communication between sump container 32 and condenser 22 through normally (during steam generation) open sump valve 44, and conduit 46 provides communication between sump container 32 and startup pump 48 (e.g., a centrifugal pump, a vanetype pump, etc.) through normally open sump valve 50. A three-way feed pump bypass valve 52 is located between startup pump 48, feed pump 12, and feed pump bypass line 54, and is normally positioned to close feed pump bypass line 54, connecting sump container 32, startup pump 48, feed pump 12 and boiler 14 in sequence. Feed pump check (one-way) valve 56 is located between boiler 14 and feed pump 12. Expander bypass line 57 between boiler 14 and condenser 22 includes three-way expander bypass valve 58, which normally connects boiler 14 with steam throttle 18.

As best shown in FIG. 2, sump heater assembly 60 consists of a chimney 62, within which is enclosed a wick-type burner 64, having a fuel chamber 66, fillable from fuel tank 24 through an auxiliary fuel line 68 and solenoid operated valve 70. A temperature sensor 72 in sump 32 is arranged to operate a solenoid control indicated at 74, which in turn operates both valve 70 and an igniter (not shown) for burner 64 drawing power therefor from the vehicle storage battery.

A hermetically sealed tubular pipe 76, containing a charge of water, or other suitable vaporizable fluid, has a bulb at its lower end 78, outside of container 32 and is located to be heated by wick burner 64. The pipe 76 extends at an inclined angle into a water-filled openended shroud 80 located in sump container 32.

Various system components are traced by thaw or warm-up lines. Feed line 39 is formed, as shown in FIG. 4, of a freezable elastomeric outer tubing 81 within which is embedded a small electrical heating coil 82. Steam lines 83 and 84 trace feed pump 12 and expander 20, respectively, are connected at one end, through normally closed valves 85, 86, respectively, with the steam outlet of boiler 14, and, at their other ends, empty into the condenser hot well. Such lines provide for immediate warm-up of these system components as soon as the boiler 14 is charged-and fired. A heating line 88 is located within water tank 42, and may be, e.g. a tube, connected to the engine oil supply to circulate hot engine oil through the water tank, a steam line, or

simply an electrical heating coil operated by the engines conventional electric generator or alternator. Correspondingly, feed 'line 39 could be traced with a hot oilline, in lieu of the illustrated electrical coil.

In operation, when the system is to be shutdown, burner 16 is extinguished and throttle valve 18 is closed, so that expander20 and feed pump 12 stop, but

with the steam pressure in boiler 14 remaining high. Feed pump bypassvalve 52 is then switched to open feed pump bypsssline 54 whereupon the steam pressure in boiler 14 forces the water in boiler l4 through bypass line 54, valve 52, startup pump 48 and open valve '50 into sump container 32. The water in condenser 22 drains by gravity through open valve 44 into sump container 32. The feed pump drain valves (not shown) then are opened to drain feed pump 12 through valve 52, startup pump 48 and valve 50, into sump container 32. After drainable water has been drained from the feed pump 12, boiler 14, various steam lines and other components which would be damaged by expansion therein of freezing water (including, e.g., the various narrow tubing lines in the condenser but not necessarily the water reservoirs therein), valves 44 and 50 are closed. The remainder of the system is thereby closed to sump container 32 to prevent migration of water from the container 32 to any colder regions of the system.

During shutdown at sub-freezing temperatures the warm water in sump container 32 and in water tank 42 will cool. Whereas the water in water tank 42 is allowed to freeze, sump container 32 is provided with a sensor 72 which detects when the sump water therein reaches a predetermined low temperature above freezing. Solenoid control 74 then opens fuel valve allowing a predetermined charge of fuel to flow from fuel tank 24 to the fuel chamber 66 of wick burner 64. The amount of fuel can be regulated, e.g., by a float operated check valve or simply by proper timing of the solenoid control 74. Since the burner is provided with a fuel charge only when needed, accidental ignition or evaporation of fuel is prevented. Actuation of solenoid 74 also actuates an igniter for burner 64. The igniter can remain on for a timed period or be thermostatically deactivated by the burner flame. Sincethe burner will remain on only until its fuel supply is exhausted, it need not be otherwise extinguished. The fuel charge to the burner is preferably chosen to be sufficient to heat the water in container 32 back to about lF. When the burner 64 ignites, the pipe 76 is heated by the burner flame, and water in the lower bulb evaporates up into the pipe heating the water in sump 32, and is condensed. The condensed water in pipe 76 then drains by gravity back into the lower bulb. When the burner 64 is off, the water collecting in the lower bulb will freeze, dropping the pressure of the remaining water vapor as low as 0.002 psia at 40F. The low desnity of the water vapor diminishes its effectiveness as a heat path, and the downward density gradient from the warm sump to the cold exposed tip essentially eliminates natural heat convection out of the warm sump along the pipe. The pipe 76 thus acts, in effect, as a heat check valve passing heat rapidly into the water when needed, and preventing reescape of heat back along the pipe. Combined with an insulated sump as shown, the heating system described provides a non-frozen water supply in an efficient, economical and simple manner. The shroud 80 provides circulation of the warmed water during the heating period, and enables the pipe 76 to be raised off the bottom of the sump so that additional ground clearance can be gained for the burner 64 in motor vehicle installations. I

To start up the system again, when an appropriate ignition switch is turned, valves 44 and 50 are opened, and expander bypass valve 58 opens bypass line 57, all utilizing power from the engine storage battery. The burner air and fuel pumps and blower are turned on, burner 16 is fired, and'valve 38 is opened to pass some air from pump 15 through air line 37 and inlet port 36, to expand bladder 35. Water is thereby displaced from container 32 through line 46v into startup pump 48, priming this pump. Startup pump 48is then turned on to fill boiler 14 through the feed pump bypass valve 52 and bypass line 54 to a preselected level sufficient to charge the boiler. All of these components are operated or turned on by power from the storage battery. Low quality steam passes into condenser 22 through the open expander bypass line 57, bypassing expander 20. Valves and 86 are then opened (e.g., thermostatically by steam in the boiler outlet lines or electrically in a timed sequence) to draw some low quality steam through the steam line 83 tracing feed pump 12 and the steam line 84 tracing expander 20, thus warming these components. The condensed steam is returned to the condenser hot well.

After pump 12 has been warmed, bypass valve 52 is switched (thermostatically by a pump temperature indicator, or in a timed sequence chosen to provide sufficient pump warm-up), opening feed pump 12 to startup pump 48 (and closing bypass line 54) which primes feed pump 12. Expander bypass valve 58 is also switched to close the outlet of boiler 14 both to the expander 20 and to condenser 22, and the valves 85, 86 are closed, thus causing steam pressure to build in the boiler. One-way check valve 56 prevents back-flow from the boiler inlet. When sufficient steam pressure and temperature have been thereby built up in the system, expander bypass valve 58 is switched (by an appropriate temperature or pressure sensitive control) to open boiler 14 to steam throttle l8, and steam throttle valve 18 (or an idle bypass) is then automatically sequentially (or thermostatically) opened. Expander 20 turns over and begins to idle, which starts up feed pump 12, which then takes over supplying water to boiler 14 through check valve 56 from container 32. As the entire system warms up, oil cycling through coil 88 in tank 42 will thaw the water therein to provide the necessary make-up water for replenishing container 32 as needed through water pump 41 and valve 40. Current may be drawn from the generator or alternator of the system to energize coil 82 for thawing feed line 39.

The water capacity of sump container 32 is chosen to be sufficient to supply inventory for the entire system including the feed lines, the hot wells of condenser 22, the pumps, boiler 14 and expander 20. As an example, if the boiler 14 has a capacity of 165 cu. inches (slightly more than half of this is normally occupied by water, the rest by steam) twice the steam generator capacity, or 330 cu. inches should be sufficient volume for the container 32. l

A cube having this volume has 2 sq. ft. of surface area. If this cube (and the various piping penetrations) isinsulated with 1. inch of polyurethane foam, such insulation would allow at least 24 hours at -20F before freezing temperatures were reached in the sump, Doubling the insulation thickness would approximately double the time. Other insulating systems can also be used, provided they are sufficiently reliable, particularly under expected repetitive shock loading.

The combination of small water inventory and good insulation for sump container 32 minimizes the energy expenditure required to keep the sump water above freezing temperatures for extended periods.

If, for some reason (lack of fuel, e.g.) the sump heater assembly fails, the water in container 32 may freeze. To take account of such a malfunction, the container 32 is formed with sloping sides 34 to allow for upward expansion of the water during freezing.

Startup pump 48 is capable of initiating system operation even under sub-freezing ambient conditions. In lieu of draining the pump as shown, the pump could be located in the container 32 itself, and designed so as to be freezable without damage in case of burner malfunction (e.g., as a centrifugal pump having both casing and impeller formed of elastomer). The container 32 needs no bladder 35 or air supply line 37 if the pump is so lo cated, since the pump will always be primed.

Water tank 42 is also constructed to avoid structural damage when the water contained therein freezes to the expanded ice state, in having sloping side walls, in the manner of sump container 32, and may also have similar insulation. FIGS. 5a and 5b show another construction, suitable not only for water tank 42, but for any other system compartment or container which must be designed to withstand ice formation. A container 90, provided with suitable exemplary access conduits 91, has a resiliently compressible, substantially non-water absorbent core 92 (formed, e.g., of an elastomeric foam such as silicone or polyurethane foam, rendered non-absorbent by a closed cell construction or application to the exposed outer surface of a watertight sealing coating or skin), and which extends in a water-tight seal out through the top 93 of container 90, allowing gas to exit the core upon its compression. As shown in FIG. 5b, the expansion due to freezing of the water to ice will be relieved by compressing of the core 92. Upon thawing, the core returns to the uncompressed form shown in FIG. 5a. Similarly compressible non-cellular materials, such as the polyvinyl chloride sold by National Research Corporation under the trade name EAR, are also suitable.

FIGS. 6a and 6b show a pipe or tube 94 useful throughout the system of FIG. 1. The pipe 94 is formed of an expandable elastomeric material, which expands, as shown in FIG. 6b, to accommodate the expansive freezing of water to ice.

FIG. 7 illustrates still another container constructed to accommodate the expansion of water to ice. An electrical heating coil 98 in the center of cylindrical container 100 (having access conduits 101) is maintained, by power applied across the terminals 102, at a temperature above the freezing point of water. Since water in cylindrical container 100 freezes slowly from the outside walls towards the center, so long as the freezing process does not become complete, and ullage still remains in the container, relatively little pressure will be exerted upon the container walls. In the construction of FIG. 7, the heat introduced by coil 98 prevents freezing in a small amount of water along the center axis of the container, allowing water to occupy the ullage even though ice might be formed in the zone between this heated water and the outer cylindrical walls of the container. Such a coil may also be used later during startup to thaw the ice in the container, simply by heating the coil to higher temperatures.

FIG. 8 shows another embodiment of a Rankine cycle steam propulsion system 110, generally similar to that of FIG. 1, like components having like numbers. Various components, such as thaw lines, have been left out for simplicity, it being understood that such may be provided as required. The sump and sump heater as sembly also have not been shown again in detail. Unlike the system of FIG. 1, however, the feed pump 120 of this system is not drainable and hence the water must be blown out of this pump to sump container 32 when the system is shutdown. The system includes two additional three-way valvesfeed pump inlet valve 122 and feed pump outlet valve 124. Inlet valve 122 is located to intercept communication between startup pump 48 and feed pump 120, and outlet valve 124 is located to intercept communication between feed pump and boiler 14. Each valve 122, 124 provides communication, through lines 134, 132, respectively, between feed pump 120 and the top header of condenser 22, and normally closes lines 132 and 134 to the condenser.

In operation, when the system is to be shutdown, burner 16 is extinguished, with the engine continuing to idle on stored steam. First valve 122, and then valve 124 (or valves 122 and 124 simultaneously) are switched to open the feed pump inlet and outlet, respectively, to condenser 22. Steam from condenser 22 enters the feed pump inlet through line 134, forcing the water in the feed pump 120 to exit ahead of the steam through line 132, so that the feed pump breaks prime. Feed pump bypass valve 52 is then switched to open feed pump bypass line 54, whereupon the steam pressure in boiler 14 forces boiler water back through line 54, pump 48, and valve 50 into sump 32. Valves 44 and 50 are then closed, sealing the sump from the remainder of the system, as before. The water in sump 32 is kept non-frozen as before.

To startup the system of FIG. 8, valves 44 and 50 are opened (bypass valve 52 is still in the position bypassing the feed pump) and feed pump valve 122 is closed to the condenser. Feed pump valve 124 remains open to the condenser. The burner is fired and startup pump 48 fills boiler 14 through the feed pump bypass line 54 to a preselected level. Valve 58 is set to permit low quality steam to pass into condenser 22 through the expander bypass line 57, while the feed pump 120 and expander are warmed by steam lines as before. Bypass valve 58 is then closed, closing the boiler outlet 14, and

feed-pump bypass line 54 is closed by valve 52. When sufficient steam pressure builds in the system, expander bypass valve 58 is switched to open boiler 14 to steam throttle l8, and steam throttle valve 18 is opened. Ex-

- pander 20 turns over, starting feed pump 120. The feed pump 120 is primed by displacing water from startup pump 48 to the condenser 22, which, is at low pressure. Feed p'ump' outlet valve 124 is then switched to close the feed pump outlet to the condenser, openingit to the boiler, completing the startup cycle;

The various feed lines and compartments of this system may be constructed and insulated as provided above with reference to the systems of FIGS. 1 to 7.

In the embodiment of FIG. 9, the sump heater assembly 60 is eliminated, and a freezable sump with a rapid thaw capability is utilized. This sump has two separate sump containers, 136 and 138. The sump container 136 is generally constructed like sump container 32 (although it could have a slightly smaller capacity so that the combined capacity of the two sump compartments is about that of sump compartment 34 of FIG. 1) withinsulation to prevent freeze during normal overnight shutdown, or even during longer periods of time. The sump container 136 may also include compressible components such as shown in FIG. 5 above, or a thawed core such as shown in FIG. 7. The system may be otherwise identical to that shown in FIG. 1 or in FIG. 8, that of FIG. 8 being the one illustrated, and like components having like numbers.

The sump container 138 is sized to contain an amount of water sufficient to start the boiler 14, but not to start the whole system (e.g., insufficient to prime feed pump 120). The container 138 is filled at shutdown, such as by gravity through the conduit 139 and check valve 139a into sump container 136, and is in communication, through line 140 and valve 141, with the pump bypass line 54. An air line 142 feeds sump container 138 through normally closed valve 142a from air pump 15.

FIGS. 10 and 11 show one embodiment of the container 138 in more detail. A pressure tight housing 143 encloses a coiled tube 144 formed of an electrically conductive elastomeric material such as a graphiteloaded plastic (or a flexible tube with an embedded heating wire) having an internal capacity equal to the water charge. The tube 144 fills with water from sump container 136 through check valve 139a while the system is being shutdown. The water in tube 144 is allowed to freeze, with the flexible eleastomeric tube expanding as required. The two ends of the conductive tube 144 are electrically connected through terminals 145 to the system storage battery. An air inlet 146 is provided to the interior of housing 143 from air line 142.

In operation, all of the water in the system, including that in the two sump containers 136, 138b is allowed to freeze during shutdown. Automatic startup is provided by thawing quickly and at a small energy expenditure the small charge of water in container 138. In particular, to start the system current is passed through the .conductive tube 144 (or, an embedded heating wire) whose resistance causes 1 R heat to be dissipated within the interior of the tube, melting the ice contained therein. The tube diameter is chosen so that the thawing process will proceed rapidly. (For example, a V4 inch diameter tube with a wall temperature of 250F will melt the contained ice in 11 seconds, a k inch diameter tube 45 seconds.) After a suitable delay (to complete thawing in container 138) the burner 16 is fired and the fuel atomizing air pump 15 is turned on. Air valve 142a is opened and valve 141a is opened (thermostatically in response to water temperature in tube 144m in accordance with a timed sequence). Air from pump 15 is pumped into the interior of the housing 143 to provide a pressure of, say, 5 to 10 psi therein. This external pressure collapses the walls of tube 144, forcing the liquid water to flow through line 140 and valve 141 directly into feed pump bypass line 54, and thence to boiler 14. The check valve 139a in the line between containers 136 and 138 prevents back flow into the sump container 136. Boiler 14 is then charged, and valve 44 is opened, circulating low pressure steam throughout the system thaw lines, and

through the condenser 22.

Not only is this steam used to thaw the feed pump and expander as before, but the condensed hot water passing from the condenser 22 back into the container 136 through the open valve 44 rapidly thaws the water in sump container 136. When the container 136 is thawed, valve 50 is opened and startup pump 48 is then primed (the steam pressure forcing water from sump container 136 into line 46). The system is otherwise totally warmed and started as set forth for the systems of FIGS. 1 and 8. Only about watt hours of energy (about one-tenth of the capacity of a conventional 12 volt I00 amp-hour lead acid storage battery) are required to thaw 1 quart of water, which is normally an adequate boiler charge for starting an automobile steam propulsion system.

Thus, in none of the heretofore described embodiments has any part of the steam propulsion system been exposed to any working fluid other than pure water. And yet the systems may be rapidly started up, at very low energy expenditure, even under extreme subfreezing conditions.

In the system of FIG. 12, however, an antifreeze additive is mixed with the drained sump water, and the sump water is then separated from the antifreeze prior to entering the system.

FIG. 12 illustrates such a Rankine cycle steam propulsion system 150. This system is in many respects similar to that heretofore described, with reference to FIG. 1, like parts having the same numbers. Various components, such as thaw lines, have been left out for simplicity, it being understood that such may be provided as required. This system has both a shutdown sump container 152 and a recirculating sump container 154, of which at least sump container 154 is insulated and shaped to allow for expansion of freezing water therein. The capacity of sump 154 is conveniently chosen to provide an amount of system water about that contained in the sump container 32 of FIG. 1, and the capacity of sump 152 is greater than that of sump 154. Sump containers 152 and 154 are in communication, through valves 156, 158, respectively, with startup pump 48, and feed pump 12. A separator 161 is located between the heater region 162 and the superheater region 164 of boiler 165. The boiler (both regions) is fired by burner 168. The separator has two outlet lines 172, 174 of which 172 leads to superheater region 164 and 174 leads back to shutdown sump 152 through valve 175. Such a separator passes vapor to the superheater 164 through line 172 and liquid back to the sump through line174. Lines 172a and 174a, shown in dotted outline, illustrate conduits for a separation designed, instead, to pass liquid to superheater 164 (through line 172a) and vapor to the sump (through line 174a). The outlet of boiler region 162 can be directly connected to the inlet of superheater region 166 through separator bypass line 176 and separator bypass valve 177. An expander 20, steam throttle 18, expander bypass line 57, expander bypass valve 58, condenser 22, and normally open valve 178 complete the steam cycle. A water tank 42 is in communication through pump 41 and valve 40 with recirculating sump container 154. A temperature sensor 181 in recirculating sump container 154 is connected to thermostatic control 182 for controlling valves 156 and 158. Shutdown sump 152 contains a mixture of water and an antifreeze additive which lowers the freezing point of water, and which has a sufficiently different volatility so as to be separable from the water in separator 161 by simple or fractional distillation. An antifreeze reservoir shown in dotted outline at 184 may also be provided, in communication with separator 161 and shutdown sump 152 through conduit 179.

In operation, when the system is shotdown, shutdown sump 152 contains non-frozen water (such as slush), whereas recirculating sump 154 contains only water. The entire system water is drained into one or the other of these sumps, preferably into sump 154 in accordance with a previously described or other suitable shutdown procedure. The valves 156 and 158 are closed and remain closed so long as the insulation of sump 154 is sufiicient to keep the water therein above a predetermined low (but above freezing) temperature. Valve 178 is also closed to prevent water migration to system cold points during shutdown. When this predetermined low water temperature is sensed in recirculating sump 154 by sensor 181, thermostatic control 182 opens valve 156 and 158 to allow the water from sump 154 to flow into shutdown sump 152 where it mixes with the antifreeze additive. Thus, the system will maintain, even during prolonged shutdown at subfreezing temperatures, a total supply of non-frozen water.

To startup the system, valves 156 and 178 are opened (valve 158 remaining closed), startup pump 48 (primed as in FIG. 1) is electrically turned on, and the boiler is fired. Pump 48 pumps the waterantifreeze mixture through feed pump bypass valve 52 and bypass line 54 to boiler region 162 to increase the temperature of the mixture so that the water and antifreeze are separated into liquid and vapor phases in separator 161. The water vapor-containing phase is passed out of line 172 to superheater region 164. The antifreeze-containing liquid phase is returned to sump 152, (or led to an antifreeze reservoir 184 where it can be stored until the next system shutdown). Steam from superheater 164 is then fed through expander bypass valve 58 and bypass line 57 to condenser 22, and into recirculating sump 154. Since valve 156 is open and valve 158 is closed, recirculation sump 154 will begin to fill with pure water, and the water content of sump 152 will be gradually reduced. The initial steam pressure is also used as heretofore described to thaw system components. If, due to some malfunction in the ther mostatic control, water has frozen in recirculation sump 154, the entering steam will also rapidly thaw that water. It is well to provide in shutdown sump 152 at shutdown a sufficient water charge to startup the system to guard against such malfunction.

When the amount of water remaining in sump 152 v has reached a predetermined low level (or that in sump 154 a predetermined high level and temperature), so that sump 154 now contains water to startup the system, valve 158 is opened, and valves 156 and 175 are closed, so that pure water-containing recirculation sump 154 is substituted for shutdown sump 152 in the steam cycle. The expander 20 and feed pump 12 are then started as heretofore described for other systems. Separator 161 can, at this point, be shut out of the system by switching valve 177, leaving direct communication between boiler 162 and superheater 164, or separator 161 may remain in the cycle for a longer time (or even permanently) to purge residual antifreeze from the system.

If the antifreeze additive is to be less volatile than water so that it will remain in the liquid phase of separator 161, either organic liquids or inorganic salts may be used. Of these, the inorganic salts have the advantage that lesser amounts will be required. Organic fluids must have a high molecular weight to remain in the sump during water, boil off, and therefore would have to exist in a predominant amount in the shutdown sump.

The suitable water-soluble inorganic salts are wellknown, and include low molecular weight species such as lithium bromide, and lithium chloride, and thehigher molecular weight diand trivalent salts, such as calcium chloride and magnesium chloride.

Useful high boiling organic liquids include glycerol and other glycols. Since these liquids will be entirely separated from the water put through the cycle, that they would be otherwise decomposable, under the high cycle temperature, to form non-condensible gasses, does not effect their utility. Neither, therefore, will superheat temperature limits have to be lowered to inefficient temperatures below 750F.

It is contemplated that the system of FIG. 12 may also be utilized with antifreeze additives having a higher volatility than that of water. These would be recovered in the vapor phase of separator 161. Since such antifreeze additives could be a minor liquid component compared to water, and also have a latent heat of vaporization less than that of water, less energy is required to effect the separation of these volatile antifreeze additives. One suitable low molecular weight, high volatility antifreeze is methanol (25 percent by weight solution in water freezes at C). The heat necessary to boil away the methanol from a solution which is percent methanol antifreeze by weight and contains one pound of water (assuming a modest reflux ratio during the batch rectification) is less than one quarter of the amount needed to boil away the pound of water. A modest flash-off of methanol into the rest of the system before shutdown aids in preventing freezing of hard-to-drain components (although some minor adjustments to the startup and shutdown cycles might be required).

In any of the above-described systems, other insulating or non-freezing procedures can be effectively utilized. For example, since ice having dissolved air ruptures very easily and upon expansion during freezing does not exert as high stress as does air-free water, if air is introduced into a sump during shutdown procedures (e.g., from the electrically operated burner blower) so as to saturate the sump water with air, stress generation on the sump walls at sub-freezing temperatures can be considerably reduced.

Other embodiments will appear to those skilled in the art and are within the following claims.

What is claimed is:

l. A winterized steam propulsion system which utilizes water as the working fluid comprising:

, a boiler, an expander, a feed pump and a condenser;

means for storing a supply of water sufficient to operate said system and to provide for make-up of leakage losses from the system, including first water storage means having the capacity to contain water frozen therein without damage to said means and second water storage means provided with means to provide substantially immediately on demand at ambient temperatures below the freezing point of water a supply of non-frozen water at least sufficient to charge said boiler;

means operative on shutdown of said-system to store substantially all of said supply of water needed for operation of said system in said second storage means and to store substantially all the remainder of said supply of water in said first storage means;

means operative on startup after shutdownat ambient temperatures below the freezing point of water to fire said boiler and to pass thereto said supply of non-frozen water from said second storage means; and

means for utilizing the steam produced from said non-frozen supply by said boiler to place said system in full operation.

2. The system of claim 1 wherein said second water storage means is provided with heating means for heating water therein sufficiently to maintain said supply of non-frozen water during shutdown of said system at ambient temperatures below the freezing point of water.

3. The system of claim 2 wherein said second water storage means comprises a barrier of thermal insulating material substantially enclosing the water stored therein.

4. The system of claim 2 including sensor means for continually sensing the temperature of water in said second storage means during shutdown of said system, and said heating means includes control means responsive to a predetermined low but above freezing temperature sensed by said sensor to activate said heating means at least intermittently during shutdown of said system.

5. The system of claim 2 wherein said heating means comprises a hermetically sealed tubular member protruding into said second storage means and containing a vaporizable liquid occupying substantially less than the total volume of said member, said member being arranged with its upper end within said second water storage means and its lower end outside of said second water storage means, and constructed and arranged with a liquid flow path between said ends providing, normally, drainage of substantially all liquid in said member to the lower end thereof, and a heating element for heating the lower end of said tubular member to vaporize said liquid therein to supply heat to the.

upper end of said member, and thereby to the water in said water storage means.

6. The system of claim 5 wherein said second water storage means comprises a barrier of thermal insulating material substantially enclosing the water in said storage means, and said tubular member is arranged to have its lower end disposed outside of said barrier.

7. The system of claim 6 wherein said tubular member is arranged to contain substantially all of the vaporizable liquid therein in a liquid phase contained in a region of said tubular member located outside of said barrier. v

8..The system of claim 1 wherein said second water storage means comprises at least first and second storage compartments, said first storage compartment being constructed and arranged to contain a supply of water sufficient to charge said boiler, and said second storage compartment being constructed and arranged to contain the remaining water in said second water storage means, and said system includes first conduit means between said first storage compartment and a water inlet to said boiler, and second conduit means between a steam outlet from said boiler and said second storage compartment.

9. The system of claim 8 wherein said first storage compartment is constructed to have the capacity to contain water frozen therein without damage to said compartment, and said system includes means for thawing water frozen in said compartment on demand to provide said non-frozen water supply.

10. The system of claim 9 wherein said second storage compartment is constructed to have the capacity to contain water frozen therein without damage to said compartment, and said system includes conduit means to pass steam produced by said boiler to said second storage comparment to thaw water frozen therein. 11. The system of claim 9 wherein said first storage compartment comprises an electrically conductive tube for containing said water supply, said tube having the capacity to contain water frozen therein without damage to said tube, and said tube includes means connectible to a power supply for passing current along said tube to thaw water frozen in said tube to provide said supply of non-frozen water for said boiler.

12. The system of claim 11 wherein said tube is formed of a resiliently compressible material, and said second water storage means includes an air-tight housing for said tube and a pressure supply arranged to pressurize said container sufficient to compress said tube, forcing water from said tube through said first conduit means into said boiler.

13. The system of claim 1 including warm-up conduits, said conduits arranged to pass steam produced by said boiler through said system to warm said system prior to placing said system in full operation.

14. The system of claim 1 wherein said second water storage means is constructed to have the capacity to contain water frozen therein without damage to said means.

15. The system of claim 1 wherein at least said first water storage means includes non-water absorbent, resiliently compressible material arranged to undergo compression when water therein expands to ice.

16. The system of claim 1 wherein said second water storage means is located at the low point of said system.

17. The system of claim 1 including valve means between said second storage means and the remainder of said system, said valve means operable to prevent liquid migration between said second storage means and colder regions of said system during shutdown of said system at said ambient termperatures below the freezing point of water.

'18. The system of claim 1 wherein said second water storage means comprises an antifreeze additive mixed with water in said storage means to maintain said water non-frozen at ambient temperatures below the freezing point of water, and a separator for recovering substantially immediately on demand a supply of non-frozen water from said mixture.

19. The system of claim 18 wherein said second water storage means contains at least first and second storage compartments, said first storage compartment being arranged to contain said antifreeze additive and sufficient water to provide a supply of non-frozen water at least sufficient to charge said boiler, said second storage compartment being arranged to contain only water, and said system comprises first conduit means between said first storage compartment and an inlet to said separator, and second conduit means between a water outlet from said separator and said second storage comparment.

20. The system of claim 19 including third conduit ,meansincluding valve means between saidfirst storage compartment and said second storage compartment,

and a sensor in said second storage compartment, said valve means responsive to a predetermined low, but above freezing temperature sensed by said sensor to provide water flow from said second storage compartment to said first storage compartment.

21. The system of claim 1 including a startup pump operative on startup for passing said supply of nonfrozen water to said boiler, said startup pump being located in said second water storage means and having the capacity to withstand frozen water in said storage means without damage to said pump.

22. The system of claim 1 wherein at least some components thereof, including said boiler and said feed pump, are adapted to be drainable to prevent damage thereto at ambient temperatures below the freezing point of said water, and wherein said system includes drain means automatically operable on shutdown to drain said drainable components to one of said water storage means.

23. The system of claim 22 wherein said drain means is arranged to drain said drainable components to said second water storage means.

24. A winterized steam propulsion system which utilizes water as the working fluid, which comprises: a boiler, an expander, a feed pump, and a condenser, at least said boiler and said feed pump being drainable;

water storage means arranged at the low point of said system and sized to contain the drainable water of said system,

drain means, including conduit means arranged to connect said water storage means with drainable system components, and valve means adapted, upon actuation, to close said valve means and thereby isolate said water storage means from said drainable components, said drain means automatically operable during shutdown of said system to drain said drainable components through said conduit means to said water storage means, and thereafter to actuate said valve means to close the same and thereby isolate said water storage means, means at said water storage means to provide substantially on demand, at ambient temperatures below the freezing point of water, in said water.

system in full operation.

s s a t s 

1. A winterized steam propulsion system which utilizes water as the working fluid comprising: a boiler, an expander, a feed pump and a condenser; means for storing a supply of water sufficient to operate said system and to provide for make-up of leakage losses from the system, including first water storage means having the capacity to contain water frozen therein without damage to said means and second water storage means provided with means to provide substantially immediately on demand at ambient temperatures below the freezing point of water a supply of non-frozen water at least sufficient to charge said boiler; means operative on shutdown of said system to store substantially all of said supply of water needed for operation of said system in said second storage means and to store substantially all the remainder of said supply of water in said first storage means; means operative on startup after shutdown at ambient temperatures below the freezing point of water to fire said boiler and to pass thereto said supply of non-frozen water from said second storage means; and means for utilizing the steam produced from said non-frozen supply by said boiler to place said system in full operation.
 2. The system of claim 1 wherein said second water storage means is provided with heating means for heating water therein sufficiently to maintain said supply of non-frozen water during shutdown of said system at ambient temperatures below the freezing point of water.
 3. The system of claim 2 wherein said second water storage means comprises a barrier of thermal insulating material substantially enclosing the water stored therein.
 4. The system of claim 2 including sensor means for continually sensing the temperature of water in said second storage means during shutdown of said system, and said heating means includes control means responsive to a predetermined low but above freezing temperature sensed by said sensor to activate said heating means at least intermittently during shutdown of said system.
 5. The system of claim 2 wherein said heating means comprises a hermetically sealed tubular member protruding into said second storage means and containing a vaporizable liquid occupying substantially less than the total volume of said member, said member being arranged with its upper end within said second water storage means and its lower end outside of said second water storage means, and constructed and arranged with a liquid flow path between said ends providing, normally, drainage of substantially all liquid in said member to the lower end thereof, and a heating element for heating the lower end of said tubular member to vaporize said liquid therein to supply heat to the upper end of said member, and thereby to the water in said water storage means.
 6. The system of claim 5 wherein said second water storage means comprises a barrier of thermal insulating material substantially enclosing the water in said storage means, and said tubular member is arranged to have its lower end disposed outside of said barrier.
 7. The system of claim 6 wherein said tubular member is arranged to contain substantially all of the vaporizable liquid tHerein in a liquid phase contained in a region of said tubular member located outside of said barrier.
 8. The system of claim 1 wherein said second water storage means comprises at least first and second storage compartments, said first storage compartment being constructed and arranged to contain a supply of water sufficient to charge said boiler, and said second storage compartment being constructed and arranged to contain the remaining water in said second water storage means, and said system includes first conduit means between said first storage compartment and a water inlet to said boiler, and second conduit means between a steam outlet from said boiler and said second storage compartment.
 9. The system of claim 8 wherein said first storage compartment is constructed to have the capacity to contain water frozen therein without damage to said compartment, and said system includes means for thawing water frozen in said compartment on demand to provide said non-frozen water supply.
 10. The system of claim 9 wherein said second storage compartment is constructed to have the capacity to contain water frozen therein without damage to said compartment, and said system includes conduit means to pass steam produced by said boiler to said second storage comparment to thaw water frozen therein.
 11. The system of claim 9 wherein said first storage compartment comprises an electrically conductive tube for containing said water supply, said tube having the capacity to contain water frozen therein without damage to said tube, and said tube includes means connectible to a power supply for passing current along said tube to thaw water frozen in said tube to provide said supply of non-frozen water for said boiler.
 12. The system of claim 11 wherein said tube is formed of a resiliently compressible material, and said second water storage means includes an air-tight housing for said tube and a pressure supply arranged to pressurize said container sufficient to compress said tube, forcing water from said tube through said first conduit means into said boiler.
 13. The system of claim 1 including warm-up conduits, said conduits arranged to pass steam produced by said boiler through said system to warm said system prior to placing said system in full operation.
 14. The system of claim 1 wherein said second water storage means is constructed to have the capacity to contain water frozen therein without damage to said means.
 15. The system of claim 1 wherein at least said first water storage means includes non-water absorbent, resiliently compressible material arranged to undergo compression when water therein expands to ice.
 16. The system of claim 1 wherein said second water storage means is located at the low point of said system.
 17. The system of claim 1 including valve means between said second storage means and the remainder of said system, said valve means operable to prevent liquid migration between said second storage means and colder regions of said system during shutdown of said system at said ambient termperatures below the freezing point of water.
 18. The system of claim 1 wherein said second water storage means comprises an antifreeze additive mixed with water in said storage means to maintain said water non-frozen at ambient temperatures below the freezing point of water, and a separator for recovering substantially immediately on demand a supply of non-frozen water from said mixture.
 19. The system of claim 18 wherein said second water storage means contains at least first and second storage compartments, said first storage compartment being arranged to contain said antifreeze additive and sufficient water to provide a supply of non-frozen water at least sufficient to charge said boiler, said second storage compartment being arranged to contain only water, and said system comprises first conduit means between said first storage compartment and an inlet to said separator, and second conduit means between a water outlet from said separator and said secOnd storage comparment.
 20. The system of claim 19 including third conduit means including valve means between said first storage compartment and said second storage compartment, and a sensor in said second storage compartment, said valve means responsive to a predetermined low, but above freezing temperature sensed by said sensor to provide water flow from said second storage compartment to said first storage compartment.
 21. The system of claim 1 including a startup pump operative on startup for passing said supply of non-frozen water to said boiler, said startup pump being located in said second water storage means and having the capacity to withstand frozen water in said storage means without damage to said pump.
 22. The system of claim 1 wherein at least some components thereof, including said boiler and said feed pump, are adapted to be drainable to prevent damage thereto at ambient temperatures below the freezing point of said water, and wherein said system includes drain means automatically operable on shutdown to drain said drainable components to one of said water storage means.
 23. The system of claim 22 wherein said drain means is arranged to drain said drainable components to said second water storage means.
 24. A winterized steam propulsion system which utilizes water as the working fluid, which comprises: a boiler, an expander, a feed pump, and a condenser, at least said boiler and said feed pump being drainable; water storage means arranged at the low point of said system and sized to contain the drainable water of said system, drain means, including conduit means arranged to connect said water storage means with drainable system components, and valve means adapted, upon actuation, to close said valve means and thereby isolate said water storage means from said drainable components, said drain means automatically operable during shutdown of said system to drain said drainable components through said conduit means to said water storage means, and thereafter to actuate said valve means to close the same and thereby isolate said water storage means, means at said water storage means to provide substantially on demand, at ambient temperatures below the freezing point of water, in said water storage means, a supply of non-frozen water at least sufficient to charge said boiler, means operative on startup of said system after shutdown at ambient temperatures below the freezing point of water to fire said boiler and to pass thereto water from said supply of non-frozen water in said water storage means, and means for utilizing the steam produced from said non-frozen water supply by said boiler to place said system in full operation. 